Dynamo-electric machine.



F. A. JOHNSON.

DX'NAMO ELECTRIC MACHINE. APPLICATION IILBD JAH.9',1911.

996.253, Patented June 27,1911.

UNITED STATES FREDERIC .AYRES JOHNSON, OF COLORADO SPRINGS, COLORADO.

DYNAMIC-ELECTRIC MACHINE.

Specification of Letters Patent. Patented ine 2'7, 1911,

Application filed January 9, 1911. Serial No. 601,667.

T 0 all whom it may concern:

Be it known that I, FREDERIC Arnns JOHNSON, a citizen of the UnitedStates, and resident of Colorado Springs, El Paso county, and State ofColorado, have invented certain new and useful Improve-j ments inDynamo-Electric Machines, of'

which the following is i specification.

My invention relates to dynamo electric machines, and more particularlyto machines of that type in which means are provided for varying thereluctance of the magnetic field circuit so as to produce correspondingvariations in the flux.

In my pending application, filed July 16, i

1910 Serial Number 572,362, I have shown and described severalarrangements for thus varying the flux, the generic object being to 3provide means for varying the main field, 1

while preserving a connnutating field of the proper strength andlocation to insure sparkless commutation without the necessity fornifting the brushes.

The present invention has the same broad objects in view, and is in thenature of an improvement on the arrangement shown in the above mentionedapplication.

Specifically, this invention seeks to provide more effective means forpreventing the distortion and shifting of the commutating field whentheinain field is varied, and for concentrating the flux at the point ofcommutation when the main field is 'Uzlhened.

lVith the above objects in view, the iiivcntion consists in theconstruction and arrangen'ient of parts hereinafter described. andclaimed, and illustrated in thc accompanying drawing, in which Figure lis a diagrammatic sectional clevation showing my invention as embodiedin a bipolar machine, and ljig. 2 is a similar view, showing the partsin shifted position.

Referring to the drawings in detail. relerence character 1 designates afield tramc which, for the purpose of illustration, is shown as anannular ring. Projecting inwardly from this ring in the usual manner area plurality of poles, two of such poles being shown by way of example.El designates the field coils surrounding the poles, 4 the armature, and5 the brushes resting upon the commutator.

Between cach ot' the poles aml the armature are the movable. elements.members or shoes (3, which are capable of being shil'tcd around theaxisof the armature as a center.

1. The shoes 6 may be shifted by means of any suitable or desiredmechanism. As illustrated in the drawings, these shoes may be secured toend plates, one of which is provided with an are shaped rack 8 adaptedto mesh with a worm 9, carried by a shaft 10, the outer end of which isprovided with. a. hand wheel 11. i

l Referring particularly to Fig. 1 it. will be seen that theinner faceof each pole is made up of cylindrical surfaces having two diti'erentcenters of curvature. The portions A, B, and A, B, of the poles are cuton the are of a circle of which the axis, C, of the armature is thecenter, while the remaining portion of each pole face such as indicatedas extending from B to l) is cut on the arc of a circle of which C isthe center. The t corresponding portion B, I) of the other i pole faceis cut on the arc-o't' a circle having its center symmetrically locatedat a point diametrically opposite from C, the radial i lines of whichhave been omitted for the l sake of clcarness. It. will thus be seenthat each pole face is cut partly concentric and partly eccentric withthe armature. It will also be noted that the shittable members 6, asclearly shown in Fig. l have their outer peripheries corresponding incontour with the pole faces. and their inner surface concentric with thearmature. 'll cretore each men'ibcr (3 is made up of a cylindrical segment, comprised between concentric arcs, and a wedge shaped segmentcomprised be tween eccentric arcs.

produce the maximum main licld flux through the arn'iaturc, that: is,this figureshows the parts arranged tor the lowest speed of thearmature, it' the machine is a variable speed motor. Fig. 2 shows themembers (3 shifted to the extreme high speed position, in which the mainflux through the armature is a minimum. This \vealwning of the fieldresults from the production of an air gap 7 betweei'i the eccentricportions of the polclace and shoe, thereby greatly increasing thereluctam-c. it. will be observed however, that, in this position and inall intermediate positions, the concentric portions of the shoe and poletacc remain in intimate contact, thus atl'or'ding a ready path for thellux at one side ol" the pole face. This results in concentrating thellux at the connnutating point adjacent the brushcs 5,

In Fig. l the parts are in a position to as clearly shown in Fig. 2,thereby producing substantially sparkless commutation at all speeds ofthe motor. It will be further observed that,.since the movement of theshoes 6 takes place in a direction concentric with the are A, B,concentric with the armature, any movement whatever will cause aseparation of the shoe and pole face along the eccentric arc B, D, andthat this separation increases rapidly as the shoe is move Thuscomparatively small movements of the shoes produce relatively largevariations in the reluctance and consequent flux values. It willbeparticularly noted, however, that in all positions of the shoes anunbroken path for the flux is afi'orded at the point of commutation.

It will thus be seen that by the above described employment of polefaces partly eccentric and partly concentric with the armature, I haveprovided a very effective means of weakening the main field whilepreserv ing the intensity of the commutating field, and it is thoughtthat the advantages of my improved construction will be readilyappreciated by those skilled in the art.

What I claim is:

1. In a dynamo electric machine, the combination with an armature, of afield structure having a pole, part of the face of said pole beingconcentric with said armature, and part being eccentric therewith, anda. shiftable member arranged between said pole f, cc and armature.

2. In a dynamo electric machine, the combination with an armature, of afield structure having a pole, the face of said pole being made up of aplurality of cylindrical surfaces each having a different center ofcurvature, and a shittable member arranged between said pole face andarmature.

3. In a dynamo electric machine, the combination with an armature, of afield structure having a pole, the face of said pole being made up of aplurality of cylindrical surfaces each having a different center ofcurvature, and a shiftable member arranged between said pole face andarmature, the outer periphery of said member conforming with the contourof said pole face.

4. In a dynamo electric machine, the combination with an armature, of afield structure having a pole, the face of said pole being made up of aplurality of cylindrical surfaces each having a different center ofcurvature, and .a shiftable member arranged between said pole face andarmature, the outer periphery of said member conforming with the contourof said pole face, and the inner face of said member being concentricwith said armature.

5 In a dynamo electric machine, the com bination with an armature, of afield structure having a. pole, the faceof said ole be ing made up of aplurality of cylindrical surfaces each having a difierent center ofcurvature, one of such centers co-inciding with the axis of thearmature, and a shiftable member arranged between said pole face andarmature.

6. In a dynamo electric machine, the combination with an armature, of afield structure having a pole, the face of said pole be ing cut partlyconcentric and partly eccentric with said armature, and a shoe shiftablearound the axis of the armature as a center, and having concentric andeccentric portions corresponding-with those of the pole piece, thearrangement being such that, when in one position, said shoe is incontact with the entire face of the pole, while, when in otherpositions, said parts are in contact at their concentric portions only,an air gap being formed between their eccentric portions.

In testimony whereof I aflix my signatu e in presence of two witnesses.

FREDERIC AYRES JOHNSON. Witnesses i C. REYER, F. N. France.

